Ewing's Analytical Instrumentation Handbook, Fourth Edition

Nelu Grinberg, Sonia Rodriguez, Nelu Grinberg, Sonia Rodriguez

• Editorial: CRC Press
• Año: 2019
• ISBN:
  9781351644310
• Edición: 4
• Categoría: Medicine
• Categoría: Pharmacology

This handbook is a guide for workers in analytical chemistry who need a starting place for information about a specific instrumental technique. It gives a basic introduction to the techniques and provides leading references on the theory and methodology for an instrumental technique. This edition thoroughly expands and updates the chapters to include concepts, applications, and key references from recent literature. It also contains a new chapter on process analytical technology.

1The Laboratory Use of Computers

Wes Schafer and Zhihao Lin

Contents

1.1Introduction

1.2Computer Components and Design Considerations

1.2.1Motherboard/CPU

1.2.2Memory/Cache

1.2.3Disk Storage

1.2.4Video (Graphics Card and Monitor)

1.2.5Other Peripherals

1.3Computer Maintenance

1.3.1Performance Monitoring

1.3.2Virus Protection

1.3.3Backup and Recovery

1.4Data Transfer/Instrument Interfaces

1.4.1Transducers

1.4.2Analog Signal Transmission

1.4.3Analog Signal Filtering

1.4.4Analog-to-Digital Conversion

1.4.4.1Sampling Interval (Rise Time)

1.4.5Digital Signal Transmission

1.4.5.1Point-to-Point Communication (Serial, Parallel)

1.4.5.2Short Distance–Multiple Device Communication

1.4.5.3Local Area Networks (LANs)

1.4.6Digital Data Filtering

1.5Data Analysis/Chemometrics

1.5.1Multivariate Calibration

1.5.1.1General Introduction

1.5.1.2Multiple Linear Regression

1.5.1.3Factor Analysis–Based Calibration

1.5.2Pattern Recognition

1.5.2.1Mapping and Display

1.5.2.2Clustering

1.5.2.3Classification

1.5.2.4SIMCA

1.6Data Organization and Storage

1.6.1Automated Data Storage

1.6.2Laboratory Information Management Systems (LIMS)

References

1.1Introduction

Although Intel’s so-called Moore’s law of doubling the number of transistors on a chip every ten years is faltering, the evolution of computers continues to be truly phenomenal. Hardware and software improvements are empowering chemist “end users” to work independently where they were once reliant on experts and centralized information technology (IT) centers. This has revolutionized some aspects of analytical chemistry especially in the fields of chemometrics and molecular modeling.

Concurrent with the increase in performance is the scientist’s dependence on computers. The computer is a valuable tool at almost all stages of experimentation. Tedious literature searches to determine the prior art of a subject are quickly dispatched by searching keywords against online databases. Computers are not only used to acquire data from analytical instruments but to conveniently control them as well, saving complex instrument parameters in method or recipe files that are easily downloaded to the instrument when needed again. Combined with automated sampling and other robotic devices, analytical instruments often work late into the night and weekend, fully utilizing expensive equipment in off-hours, and freeing the scientist to concentrate on experimental design and result analysis. Computers are also extensively used in data analysis, automatically calculating results and graphically displaying them for the scientist to best interpret. Finally they have proven themselves invaluable in the more mundane task of storing and organizing the scientist’s data for later retrieval as necessary.

This chapter is divided into two sections. The first section briefly describes the physical components of the system and their interdependence. The key attributes of each component as they relate to the performance of the system are discussed. The second section focuses on the role of the computer in each stage of the experimental process: data acquisition, data analysis, and data storage.

1.2Computer Components and Design Considerations

As one would expect, the intended use of the system should be taken into account when determining which computer should be used with a given instrument. Although computers are becoming continually faster and cheaper, it is still possible to waste several thousand dollars on system components that are simply not needed.

A simple ultraviolet (UV) spectrophotometer with associated software to determine absorbance and calculate Bier’s law curves is unlikely to tax a modern personal computer. The amount of data produced by the instrument and its subsequent processing can be handled by a relatively low-end computer with a relatively small hard drive. A Michelson interferometer-based infrared spectrophotometer that must perform Fourier transforms of the data would require more resources. If it is to also perform complex chemometric calculations, processing time would probably benefit from a higher-end PC. If the application is to continually compare collected spectra to a library of spectra on the hard drive, it would benefit from a system with quick disk input/output (I/O). High-end molecular modeling and quantum calculations to support structure elucidation and mechanistic calculations still severely tax workstations typically available to the chemist and may require so-called supercomputers to complete.

Although instrument manufacturers have little incentive to sell an underpowered computer with their instrument as it also reflects poorly on their product, marketing considerations and the desire to avoid testing newer model PCs may mean the PC offered by the instrument vendor is not the optimal one. The computers offered by instrument vendors are also often priced at a hefty premium when compared to market prices.

Still the decision to purchase the computer from the vendor or separately must be made on a laboratory-to-laboratory or even instrument-to-instrument basis. If the laboratory has little experience with the computer, operating system, and application software, then purchasing the computer from the vendor and including it on the vendor’s service/maintenance contract is a sensible approach. This provides a single contact point for all instrument and computer issues. The instrument and software were also presumably thoroughly tested on the computer offered. If, however, a service contract will not be purchased with the instrument or if the PC is not included in the service contract, it is often advantageous to purchase the computer separately.

Frequently a laboratory’s IT organization places a number of additional requirements on the computer and the configuration of its operating system. If the instrument and its software place no special requirements on the computer, it may be best to obtain one of the computer models supported by the organization’s internal IT group.

1.2.1Motherboard/CPU

The motherboard is the unifying component of the computer. It contains the central processing unit (CPU) as well as the system bus, which is the means by which the CPU transfers data to other key components such as the memory and the hard drive. It also contains the expansion slots and communication ports that interface the computer to its peripherals such as the monitor, printer, and the laboratory instrument itself. A growing number of these peripherals (e.g., video adapters and network interface cards) are being integrated onto the motherboard as PC manufacturers search for more ways to lower costs.

Although the motherboard and CPU are two separate components with different functions, they are completely interdependent. The motherboard contains the support chips for the CPU, which dictates its architecture as well as the number of bits it processes at a time...